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Technical Cement Forum / secondary air temperature

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faslan 17/03/2010 14:01:04

secondary air temperature

Hi everyone,

I've been following the forum for a long time. Thank you very much for your experiences and valuable info.

I'm applying a heat balance around clinker cooler. While doing this I wonder about the optimum secondary air temperature. Because of bad working of the grate cooler, the secondary air temperature fluctuates from 800-1150 degrees celcius. What will happened if we could stabilise this temperature at 1200 or 900 C. The high temperature can lead low air flowrate however good flame and high combustion efficiency etc.. 900 C can be good for outlet plates of the kiln and high flowrate of air which means high oxygen. We don't have any idea about gas O2 content at the kiln inlet but after ID fan it is around % 4. Can you make a comment?

Best regards,

Firat Aslan

Michael Clark 18/03/2010 09:21:13

You need to stabilise the secondary air temperature. the fluctuations are worse than if the temperature was always on the lower side. This will stabilise the combustion and the whole operation of the kiln. I suggest setting a feedrate and not making any adjustment for some hours and see if you can stabilise the kiln. It is much better the stabilise at 900C than have fluctuations.

Best regards

Michael Clark

faslan 18/03/2010 14:29:26

You are right Mr. Clark. I'm sure that instead of fluctuation the stabilised low temperature will be better. However, i tried to ask if we could increase the temperature to 1100 C and stabilise it at that temp. What's gonna be happened? As the temperature increase the petcoke will burn better. what about the oxygen? as we increase the temperature for the same volumetric flowrate oxygen flow will decrease..

Which will be better 900 C or 1100?

Thank you.

ovancantfort 18/03/2010 16:13:45

If secondary air temperature increases, your kiln oxygen will not decrease. In fact, it may even increase a little bit.

Remember that the amount of oxygen drawn into the kiln is given by the action of the ID fan. ID fan temperature should not significantly change when secondary air temp changes. Volumetric flow will not significantly change at ID fan.

Besides, with higher secondary air temperature, you have to burn less fuel to reach burning zone temperature (the kiln heat efficiency increases due to better heat recuperation from the cooler), hence less smoke volume generation, hence more capacity for the ID fan to draw some more air, hence increased oxygen, or better increased clinker production :-)

Best regards,

O. Van Cantfort

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